--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/basic/README.txt	Mon Jul 23 16:07:12 2018 +0900
@@ -0,0 +1,165 @@
+BASIC AND FLOATING POINT ROUTINES FOR THE 6809
+==============================================
+
+sbc09 stands for Lennart Benschop 6809 Single Board Computer.
+It contains a assembler and simulator for the Motorola M6809 processor.
+
+copyleft (c) 1994-2014 by the sbc09 team, see AUTHORS for more details.
+license: GNU General Public License version 2, see LICENSE for more details.
+
+
+
+FLOATING POINT ROUTINES FOR THE 6809
+------------------------------------
+
+They are intended to be used with the sbc09 system. These routines
+should be fairly portable to any 6809-based system. 
+
+As it is an unfinished program (intended to become a full-featured
+BASIC interpreter one day), I never released it before and I almost
+forgot about it. Fortunately it was still on a backup CD-R that I
+made in 2001.
+
+
+FILES
+- - -
+
+makeflot.c   Conversion tool to convert floatnum.src to floatnum.inc
+
+floatnum.inc Floating point constants to be included in main program.
+floatnum.src Same constants, but not converted to binary.
+
+fbasic.asm   RPN calculator with floating point (just to test the FP routines.
+	     This was intended to be part of a larger Basic interpreter,
+   	     but this was never finished).
+
+basic.asm    Tiny Basic
+basic.txt    Tiny Basic instructions
+
+It was originally planned to turn this into a full-fledged BASIC
+interpreter (maybe somewhat like BBC Basic), but this never
+happened. It is now a rudimentary RPN calculator, just to test the 
+floating point routines. Each number or command needs to be on a separate
+line.
+
+
+
+
+MAKE THE PROGRAMS
+- - - - - - - - -
+
+Simple:
+
+make
+
+
+Or in single steps:
+
+compile the helper tool ...
+
+./makeflot <floatnum.src >floatnum.inc
+
+
+assemble the FP calculator ...
+
+./a09 fbasic.asm
+
+
+assemble Tiny Basic (integer only) ...
+
+./a09 basic.asm
+
+
+
+
+RUN THE PROGRAMS
+- - - - - - - - 
+
+
+Start the board simulator
+
+../v09
+
+You should see the prompt "Welcome to BUGGY version 1.0"
+
+Type the command 
+
+xl400
+
+Press the escape character Control-]
+(e.g. on Linux for a german style keyboard Control+AltGr+9)
+
+Then you see the v09> prompt.
+
+Type the command
+
+ufbasic
+
+Now the file "fbasic" will be uploaded to the board.
+
+Type the command 
+
+g400
+
+Now you can type floating point numbers and commands (RPN style), each
+on a different line, like this
+
+2
+3
+*
+ 6.00000000E+00
+
+1
+0
+/
+
+The last calculation breaks back to the monitor.
+
+The following commands are available (see the source):
++ - * /  (the normal arithmetic operators).
+=  compare top two numbers on stack (and leave them), show < = or >
+i  round to integer (round to -Inf, like BASIC INT() function).
+q  square root
+s  sin
+c  cos
+t  tan
+a  atan
+l  ln
+e  exp
+d  duplicate number on stack
+x  exchange top numbers on stack.
+r  remove top of stack.
+
+
+
+IMPLEMENTATION NOTES
+- - - - - - - - - - 
+
+This is a 40-bit float, like many microcomputers of the 80s had,
+including the Commodore 64, the ZX-Spectrum, the BBC and others.  It
+has an 8-bit exponent and a 32-bit mantissa (with hidden leading bit).
+The basic operations (including square root) should be as accurate as
+can be expected.
+
+It does not do IEEE-754 features, such as Infinity, NaN, +/-zero and
+subnormal numbers, but appears to work quite reasonably.
+
+Trig functions deviate a few places in the 9th decimal. In particular
+sin(pi/2) shows as 9.99999998E-01 instead of 1.00000000E+00. I
+consider this acceptable and consistent with what could be expected.
+
+The Log function deviates a few places in the 8th decimal. LN(5) appears to
+be about worst-case. I find this a bit disappointing.
+
+2
+l
+5
+l
++
+e
+
+should show exactly 10, but it shows 9.99999970E+00 instead.  This is
+not caused by the exp function, but by the log of 5 (as I checked with
+Python).
+
+